[Cl-:1].[Na+].[C:3]([C:6]1[CH:7]=[C:8]([CH:12]=[C:13]([C:15]2[CH:20]=[CH:19][C:18]([CH3:21])=[CH:17][N:16]=2)[CH:14]=1)[C:9]([OH:11])=[O:10])([CH3:5])=[CH2:4].CS(O)(=O)=[O:24].[OH-].[Na+]>O>[ClH:1].[OH:24][C:3]([C:6]1[CH:7]=[C:8]([CH:12]=[C:13]([C:15]2[CH:20]=[CH:19][C:18]([CH3:21])=[CH:17][N:16]=2)[CH:14]=1)[C:9]([OH:11])=[O:10])([CH3:5])[CH3:4]To a solution of the sodium chloride salt of 3-isopropenyl-5-(5-methylpyridin-2-yl)benzoic acid (2.114 g, 4.93 mmol) in water (49.3 mL) at 0° C. was added methanesulfonic acid (23.7 mL, 247 mmol) and the mixture was heated to 50° C. After 16 h, the mixture was cooled to 0° C. and sodium hydroxide (9.86 g, 247 mmol) added. The mixture was extracted with ethyl acetate (3×). The combined organic extracts were washed with brine, dried over magnesium sulfate, filtered and concentrated. The mixture was purified by reverse phase chromatography (C-18, 95% water/acetonitrile→65% water/acetonitrile with 0.1% trifluoroacetic acid). Treatment with 2 M hydrochloric acid in diethyl ether gave the title compound as a hydrochloride salt (1.252 g). MS 272.0 (M+1).
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